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I. E. HINDMAN.

LIFTING JACK.

APPLiCATION FILED FEB-20.15MB.

Patented Sept. 23, 1919.

2 SHEETS-SHEET 1.

INVENTOR WITNESSES I. E. HINDMAN.

LIFTING-JACK- APPLICATION FILED FEB- 20. 191B.

Patented Sept. 23, 1919.

2 SHEETS-SHEET 2- I WITNESSES WMCZW reared; n. armament or BhLLnvun,rm'msirnv, rattan re nurr nauuraorumeoomremr, or r1rrsBUBeH, jrENNsrL;vnmn,n neuroneslow or rnuusvtvplvm Mm -J Specification of Lettersrateiit. Patented Sept.

Application filed. February so, 1913. Serial No. we. 1

Te all whom it may concern it known that I, ISAIAH HiNnMAN, residing atBellevue, in the county of Alle gheny and State of Pennsylva'niafhave invented a new and useful Improvement 1n Lifting-Jacks, of which thefollowing is a full, clear, and exact description, reference being hadto the accompanying drawings,

forming whi'ch-'-- Figure 1 is' a side 'elevationwith a partof thecasingremoved and showing a porpaft of this specification, in

tion of a jack embody'ing my inventiongand .Fig. 2 a similar view adlfi'erent posltion. I y mvent1onhas relation to lifting. acks,

with the parts in and more particularly to single-acting jacks which maybe operated either to raise or lower the load. The invention is more inthe patent of W. McH. Alston and myspecifically designed as animprovementupon the lifting ack described and claimed self; datedDecember 28,- 1915, No. 1,165,380.

The object of the present invention is to simplify and improve themechanism for controlling theaction of the pawls.

Referring to the accompanying draw 'in g's, in which I have illustrateda preferred embodiment of the invention and which will now be described,the numeral 2 designates the',usua l lifting bar mounted for.'verticalsald teeth to newengagmg poslt on. During the furtherdownw'ard'movement'of the trunni'oned in theframe, as indicated at 6.-

7 designates the upper pawl which is mount- ,wlth the lower cam portion19*, thereby -ed on a pivot 8, carried by theheel of the 'lever 5; and 9is the lower PflWlWhlChlS The numeralll designates anangle lever whichis pivoted at its angle portion to the frame, as indicateda't 12.Theforwardly projecting, arm of this lever has therein a curved'slot 13,whichis engaged by a stud j 14 on the shorter arm'of a reversing lever15., whose other 'arm'progects through a slot 16 in the casing inposition to be actuated.

- V ,The numeral 17 designates a cam memher-"Which is pivoted at 18 tothe other and upwardly extending arm of the lever a The member 17 isshown as being of general ttrsha p, its coneave side facing the cornerportion of the member ment with the upper cam portion 19 of the leverand having the upper cam portioh 19 and the lowerflcam portion 19 Theupper pawl 7. Is connected to' phe uppei' rearprojecting which isrigidly-secured to,

one of the trunnions 6, and which is adapted to cooperate with the camportions of the member 17 in the manner hereinafter described.

In Fig. 1, the parts are shown as being in position for the raising ofthe load with the actuating lever 5 inits upward position and ready, forthe commencement of its down or workingstroke. At this time, bothsprings 20and 21 are under some tension. As the lever 5 1s moveddownwardly, the pawl 7 fit raises the bar 2 and-pawl 9 is idle. As thelever 5 approaches the limit of its down stroke, the end of the arm 22engages the upper cam portion 19 of the member 17 and rocks said memberon the center 18 to the pe -sitionshown in dotted lines in said figure,

thereby increasing the tension on the spring 20 and decreasing thetension on the spring 21'. On the upstroke of the lever fi, the pawl 7is therefore held by its spring against the rack teeth'while it'movesdownwardly over lever 5, the arm 22 will ride out of engagemember 17,and thereafterdnto engagement shown in-full lines in Fig. 1, in whichthe tension on 'the' upper spring 20 is decreased and the tension on thelower spring 21 is increased. In the positions which theparts occupyduring the raising operations of the jack, the shifting movements of themem- "bers17 have comparatively little efi'ect upon the springs "20 and21; andthese springs are at all times under some'tension or at least arenot compressed beyond their neu- 'tral positions. In fact, in so far asthe raising action is concerned, the member 1"? may be made so as tohave practically in action upon the pawls.

In order to adapt the jack for use for lowering. a load, the lever 15 isshifted to the pesition shQWn in Fig. 2: ,t his the angle lever 11 fromtheposition shown in Fig.1 to the position shown in Fig. 2,

- thereby moving its upwardly extending arm shown in full lines in Fig;2)

- 7 will in this position of the parts be forced the load moves downwith the pawl 7 until entirely out of engagement with the rack teeth,while the lower pawl 9 will be drawn firmly into engagementwith suchteeth. As the lever 5 moves downwardly, the end of the arm 22 contactswith the upper cam portion 18 of the member 17, and said me1nher isthereby shifted on the center 18, so as to place the upper spring 20 intension and the lower spring 21 in compression. The upper pawl 7 (whichhas now been lifted to a new engaging position) is now pulled intoengagement with the rack teeth, while the engagement of the lower pawlwill be released. On the upstroke of the lever 5,

near the limit of the stroke. The arm 22 then shifts the member 17 tobring the parts to the position shown in full lines in Fig. 2, with thepawl. 7 free and the pawl 9 holding the load. y

The advantages of my invention result from the provision of theshiftable angle lever 11 and cam member 17, or their equivalents. Theprovision of these parts enables the pawl springs to be at all timesmaintained under thenecessary tension while lifting the load, butpermits them to be alternately placed in tension and compres sion whilelowering the load. The member 22 or its equivalent carried by theactuating lever provides for positively insuring the change in thenature of the spring action as the actuating lever approaches the limitof its strokes.

I do not desire to limit myself to the particular construction andarrangement of the parts as herein shown and described, since it will beobvious that various changes may be made therein within the spirit andscope of the appended claims.

I claim:

1. In a lifting jack, the combination of a lifting bar, a frame, anactuating lever pivoted to the frame, upper and-lower pawls,

one of said pawls being pivoted to the actuating lever while the otherbeing connected to the frame, a cam support pivoted to the frame, a cammember pivotally mounted on the 'camsupport, a spring connecting .eachpawl with said cam member, a member carried by .the actuating lever andadapted to engage the cam member to reverse the action of thesprings,and means for bodily connected to'the frame, a cam member pivotallyconnected to one arm of the angle lever, a spring connecting the upperarm of said cam member with one pawl, another spring connecting thelower arm of the cam member with the other pawl, a combined shifting andlocking lever for the angle lever pivotally mounted on the frame, and ahand lever connected to the locking member, substantiall as described.

3. In a lifting the combination of a lifting bar, a frame, an actuatingmember pivotally connected to the frame, an angle lever pivoted to theframe, a cam member having upper and lower arms pivoted to the anglemember, a pawl connected to the actuating lever, a pawl connected to theframe,.

a spring connecting one pawl with the up per arm of the cam member, asecond spring connecting the lower arm of the cam member with the otherpawl, a member carried by the actuating lever and adapted to alternately engage the upper and lower arms of the cam member near the endsof the movement of said lever, a shifting member pivoted to the framefor shifting the angle member to reverse the action of the jack, saidshifting member and angle member having connecting means arranged tolock the angle member in either of its shifted positions, substantiallyas described.

In testimony whereof I have hereunto set my hand.

I. E. HINDMAN.

